The invention relates to a self-centering chuck of the type having for example three or four independent jaws mounted in a hollow body for movement therein. The jaws are opened and closed by rotating a control sleeve which is threadably connected to the jaws. The chuck is utilized to tightly hold a tool bit such as a drill bit or other suitable tool or workpiece. The rotation of the control sleeve is generally controlled by means of a key inserted radially into the end portion of the hollow body of the chuck containing the jaws. The key is provided with a pinion that mates with a bevel gear formed on the end-face of the control sleeve.
In most conventional chucks, the bevel gear is formed on the end-face of the control sleeve which faces toward the front end of the hollow body whereat the tool bit held by the chuck is inserted. Therefore, the hollow body of the chuck must project out over and beyond the end of the control sleeve so as to make possible the aforementioned operation by means of the key. This projecting portion of the hollow body of the chuck has a relatively thick tapered wall because the hollow body must withstand severe radial forces transmitted to it by the jaws that tighten around the tool bit.
Most chucks have heretofore been made of metal by costly machining operations utilizing machine tools. It would be highly desirable to be able to manufacture chucks at least in part with a molded part made out of plastic for instance by means of an injection molding process.